In recent years, computing machines have been in widespread use with increasing opportunities for even those who are not well informed about computing machines to use computing machines. Such a computing machine beginner occasionally fails to solve a problem arising with a computing machine trouble and carry out periodical maintenance such as deletion of unnecessary files by himself or herself. Therefore, it is necessary to ask someone who is knowledgeable about a computing machine to carry out maintenance.
As a related technique, a non-patent literature 1 discloses a configuration of a general duplex system. The duplex system is a system in which each component element of a machine is duplicated and if one of component elements has a trouble, the other one serving as a backup system is used to continue a work, whereby enabling high availability. In such as a configuration, even if a troubled component element is being subjected to maintenance, a machine can be operated. Since the duplex system has premise that storage is always synchronized, if contents of storages of a main system and a standby system are different from each other due to rewriting a setting for an OS (Operating System) and/or an application, disk synchronization needs to be carried out by discarding an update in any one of the storages in order to return to an operation only in the main system.
A patent literature 1 (JP2004-171412A) discloses a technique that, in a thin client of an image transfer type, a VM (Visual Machine) on a server side is rolled back to a normal state, whereby maintenance is carried out.
The above related techniques have a problem that work results provided by a user during a maintenance work are lost because of disk synchronization and rollback carried out after completion of the maintenance.